The normal mitral valve exhibits almost explosive transitions between tightly sealed and widely open states. These functional conditions and transitions require intricate, synchronized, three dimensional dynamic interactions between the key elements comprising the mitral valvular-ventricular-atrial (VVA) complex: 1. Left atrium; 2. Mitral annulus; 3. Mitral leaflets and 4. Chordae tenideae, papillary muscles, and LV myocardium. Malfunction of any of these components, due to infection, cardiomyopathy, degenerative processes, congenital malformations, or coronary disease can mean progressive debilitation or even death. Some 16,000 patients require mitral valve surgery each year in the US and this number is increasing as the population ages. While many different medical and surgery therapies exist and new approaches are suggested each year, it remains difficult to evaluate their effectiveness objectively due to absence of precise knowledge concerning the instantaneous 3-D dynamics of the VVA complex throughout the cardiac cycle under both normal and pathophysiological conditions. The goal of the studies outlined in this renewal application is to provide such clinical relevant knowledge. The investigators are in a unique position to do so, as recent advances allow them to place extensive arrays of miniature radio opaque markers in all parts of the VVA complex in experimental animals, including the leaflets themselves. Using computer analysis of simultaneous, high speed biplane radiographic images of these markers, they can determine the 3-D size, shape, and motion of these structures in awake intact animals, thereby obtaining precise and reproducible data unavailable using other techniques. They propose to study all four inter-related elements of the VVA complex under: 1. Normal conditions; 2. After creation of mitral regurgitation due to: a. Acute ischemia; b, dilated cardiomyopathy or c. direct anatomical leaflet damage and 3. To determine the extent to which mitral valvular competence can be restored thereafter by mitral repair, various annular rings, or resolution of LV dysfunction. One major clinical goal is to allow more intelligent reparative to surgical methods to be engineered in the future based on more complete understanding of the mechanisms responsible for dysfunction of the VVA complex.